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 Post subject: Anyone heard of Perlite?
PostPosted: Sat Dec 30, 2017 10:31 am 
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Joined: Sun Apr 02, 2017 3:53 pm
Posts: 3
Location: Front Range, Colorado
Hello all,

I tried a search for 'Perlite' but nothing came back.

I am interested some sound absorbtion for my humble studio. Right now it is a basement studio, about 7'2" by 7'2" by 8'2" high, exposed studs on two sides, concrete on the 3rd, open on the 4th to a larger room and open joists on the ceiling. Perhaps it is not really big enough to warrant any sound control, but in the future I may be able to expand and always looking for a good deal on material. An ad near me has what they call 'perlite fiberboards', 2'x4' and sold by the pallet. Industrially, one of its purported roles is as a sound absorber.

1. Anyone have any idea on this stuff and how it compares to 703?

2. Anyone have any thoughts about this material?

Thank you for any responses!


Last edited by Red Leader on Sun Jan 07, 2018 11:45 am, edited 1 time in total.

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PostPosted: Sat Dec 30, 2017 10:41 am 
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Location: Front Range, Colorado
I also found this document, but I don't know how this compares to other sound absorbers on the market -

Some info on Perlite


Last edited by Red Leader on Sun Jan 07, 2018 11:48 am, edited 1 time in total.

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PostPosted: Sat Dec 30, 2017 1:49 pm 
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Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things! :)

That said, the graphs in that paper about perlite are not very encouraging at all. Here's a comparison of the graph in that paper, vs. the way a good rear-wall absorber would be done in a typical studio, using ordinary pink fluffy insulation and OC703:

PERLITE:

Attachment:
perlite-absorption-coefficient-graph.jpg




Fluffy + 703:

Attachment:
OC703-and-fluffy-absorption-coefficient-projection.jpg


Notice that the horizontal scales are different! The Perlite graph is linear, which is very strange in acoustics... Graphs are always log based, because human hearing is log based.... The OC703 graph is log, as you can see.

The difference is crystal clear: The perlite is only useful around 2kHz, which normally is not a problem in most studios. The fluffy and 703 goes way down low, and covers the entire spectrum. Perlite is no use at all below about 1500 Hz. Even down at 100 Hz (four octaves lower!), OC703 is still doing fine

You didn't say what you wanted to use it for, but I'm assuming the application is typical low-frequency treatment of a typical studio. So unless you an find the actual graphs for the actual specific material, and it is substantially better than what that paper shows, you can forget the Perlite stuff.



- Stuart -


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PostPosted: Sun Jan 07, 2018 11:55 am 
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Stuart,

I really appreciate your thorough response. I read the rules and went back and made some changes to my post - thank you for grace in that matter.

What I have read mirrors your response - that one of the most impactful changes one can do to their studio to manage acoustics is to manage lower frequencies when considering isolation or absorbtion.

A co-worker found some rockwool and grabbed a couple packs for me (12x 2"x4'x8' sheets) and so now my next step is to research this material and consider some appropriate applications.

I think I will still try to do some floor to ceiling bass traps out of 12-14" pink fluffy with paper backing on the front, but again, with how small the room is, I don't yet know how critical it is. I will be recording in this space, but the serious mixing and mastering will be done somewhere else. I know none of this is really ideal, but any little improvement will be welcomed.

Thank you again!

-Dave


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PostPosted: Sun Jan 07, 2018 2:17 pm 
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Quote:
one of the most impactful changes one can do to their studio to manage acoustics is to manage lower frequencies when considering isolation or absorbtion.
Right! But which of those two do you need the insulation for? Isolation and treatment (absorption inside the room) are very, very different. Many people think it's the same thing, and all called "soundproofing", but that's not the case at all. Isolation is one thing, and needs one set pf materials (mostly massive, heavy, rigid, solid, hard materials), and acoustic treatment needs an entirely different set of materials, such as light, soft, fluffy, absorptive materials.

Is this a control room, for mixing? Or a live room / rehearsal room? That's two rather different acoustic situations.

From what you say, I'm assuming that this is a tracking/rehearsal room, and that you need to get the acoustic response suitable for recording instruments. Is that right? I'd suggest that you start by doing an acoustic test of your room to see what problems you have, then install specific treatment to deal with each of those. Here's how to do the test: viewtopic.php?f=3&t=21122 That set of instructions of for control rooms, but it can also help you identify the issues in a live room.

Quote:
A co-worker found some rockwool and grabbed a couple packs for me (12x 2"x4'x8' sheets) and so now my next step is to research this material and consider some appropriate applications.
Did he actually get a genuine Rockwool brand product, or just some type of generic mineral wool insulation? People often refer to that as "rockwool", but in reality Rockwool is a brand name: mineral wool is the type of product they make.

It would help to know exactly which product he got for you: some mineral wool products are good for certain things, other products for other things, and yet other products are not much use at all for acoustics (the high density ones, for example, aren't useful).

Quote:
but again, with how small the room is, I don't yet know how critical it is.
The test outlined above will help to identify the issues. Setup your speakers on stands against the shortest wall, aimed down the length of the room, with the mic about one third of the distance across the room, at ear height.

Quote:
I will be recording in this space, but the serious mixing and mastering will be done somewhere else. I know none of this is really ideal, but any little improvement will be welcomed.
Well, the room isn't ideal, the ceiling is low, etc., but think of it this way: A room that isn't ideal is still a hell of a lot better than no room at all! :) With treatment, it can still allow you to do some recording, especially if you close-mic the instruments and keep the mics low down.

- Stuart -

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